The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.
The Unbreakable Enterprise Kernel Release 3 (UEK R3) is based on the upstream kernel 3.8.13 stable source tree. For more information about UEK R3, see Unbreakable Enterprise Kernel: Release Notes for Unbreakable Enterprise Kernel Release 3 Quarterly Update 3.
A very large number of changes have taken place in mainline Linux between 3.0.x, on which UEK R2 is based, and 3.8.13, on which UEK R3 is based. For details of all these changes, see the kernel change logs that the Linux Kernel Newbies maintain at https://kernelnewbies.org/LinuxVersions.